Impact of Co and Cu co-doping on the Structural, Electrical, Magnetic and Solar Light Driven Photo-Catalytic Properties of NiFe2O4 Nano-crystals for Crystal Violet Dye Removal

Abstract

Herein, we have synthesised cobalt (Co) and copper (Cu) co-doped Ni-ferrite Ni1-xCoxFe2-yCuyO4 nanocrystals (NCs) via the facile micro-emulsion method. The materials were analysed for various physio-chemical characterizations to investigate the co-doping (Co and Cu) effects on magnetic, structural, electrical, photo-catalytic properties. The structural analysis via Fourier Transform Infrared spectroscopy (FTIR) and X-rays diffraction (XRD) showed the successful fabrication of Co and Cu co-doped materials with cubic spinel geometry having a single phase, the crystallite size was observed in 15 to 24 nm range. The electrical response measured using current-voltage (I–V) analysis showed good electrical features, the electrical resistivity declined from 6.85×107 Ohm.cm for un-doped materials to 0.04×107 Ohm.cm for co-doped materials, which was accredited due to the synergistic effects of Co and Cu metal cations in co-doped Ni-based ferrite structures. Magnetic investigation using VSM analysis showed increased saturation magnetization (Ms 31.32 to 50.75 emu/g) and coercivity (218.76 to 406.82 Oe) because of the higher magnetic responses of Co2+ions in the co-doped spinel ferrite NCs. BET surface-area analysis showed good porosity for co-doped materials with an increased surface area of 52 to 104 m2/g on co-doping. The Tauc's plot described the decline of band-gap energies value (Egs) (1.99 eV) in co-doped (x=y=0.56) materials as compared to (2.16 eV) of the un-doped NiFe2O4 materials, which is due to more electrical responses of Co and Cu co-dopant cations that possess higher energy levels, which can stabilize the charge carrier‘s species. Furthermore, the photo-degradation using solar light showed good removal of crystal violet (CV) dye, which was almost 94.14 % by co-doped material; however, by un-doped material, it was 38.044 %. The scavenger experiment shows that the (OH⋅) hydroxyl radicals and (e−/h+) species play a prime role in the degradation of CV dye. Recycling and recoverability tests for five cycles’ exhibited outstanding stability of the photocatalyst with only 1.7 % losses in activity. Overall, our results showed that co-doped Ni1-xCoxFe2-yCuyO4 NCs materials exhibited enhancement in the magnetic, electrical, photo-catalytic properties and a decline in band-gap energy values as compared to un-doped NiFe2O4, which might have potential use in magnetic and electrical devices as well as solar-driven photo-catalyst materials for the remediation of environmental pollution.